Difference between Blender 2.8’s camera and world HDRI
Well since you seem to have cross posted this I'll just shamelessly plagiarize Brecht's answer for completeness sake.

Camera HDRIs are basic studio lights meant for fast performance with non realistic shading.

They will behave like matcaps in the sense that they are viewpoint dependent and will rotate along with the view angle.

World HDRIs behave as realistic environment maps like the ones you would use in Cycles World environment textures.

They are convenient scene lighting replacement suitable for quickly testing your model and viewing it under different lighting conditions.

Both can be easily easily user customized by adding new entries to the menu either from the user preferences by pressing the small Wrench icon, or by manually adding files to the folder Blender-2.80\2.80\datafiles\studiolights, either under a Camera, Matcap, or World subfolder.


  By Brecht
  
  Camera HDRIs are like matcaps or solid mode lighting in 2.7x, in that
  they rotate along with the camera. This ensures objects are always
  well lit and you can see their shape clearly, even if it’s not
  realistic.
  
  World HDRIs are the same as environment textures in the world, with
  light coming from the same global direction. This is the more
  realistic method, and the only one that can be efficiently supported
  for features like Eevee indirect light and light probes. For that
  reason camera HDRI’s are not available in LookDev shading mode.
  
  Naming of these features could be improved.